A floor tunnel is disposed on a floor panel, which is a floor board of a vehicle compartment (cabin) in which an occupant is accommodated. The floor tunnel is protrudingly extended along a vehicle front-back direction at the center in a vehicle width direction so as to divide the vehicle compartment between a driver seat and a passenger seat.
Conventionally, an exhaust pipe for directing exhaust gas from an internal combustion engine to a rear portion of a vehicle has been extended within the floor tunnel. However, for fuel cell vehicles which need no internal combustion engine and therefore need no exhaust pipe, it has been suggested that a hydrogen tank which is a fuel tank be disposed in place of the exhaust pipe within the floor tunnel.
Meanwhile, a seat cross member, which is a frame member, is disposed so as to extend from the floor tunnel toward a vehicle lateral end; i.e., along a vehicle width direction. An outer end portion in the vehicle width direction of the seat cross member is connected to a rocker panel which is another frame member disposed on the vehicle lateral end so as to extend along a vehicle front-back direction.
When a vehicle collides on its side (hereinafter referred to as a side collision as appropriate), a collision load is input to an inner region in the vehicle width direction. The collision load causes the rocker panel and the seat cross member to be displaced toward (stuck into) the floor tunnel located at the center of the vehicle compartment. Here, in JP 2016-130103 A, for example, a cushioning member composed of a rubber block is disposed between a hydrogen tank and a seat cross member to protect the hydrogen tank placed under the floor tunnel. At the occurrence of a side collision, the cushioning member is crushed and deformed, while functioning as, so to speak, a sacrifice for the hydrogen tank, to thereby protect the hydrogen tank.
Meanwhile, casings of hydrogen tanks mounted on vehicles are required to have a load bearing property. For example, it is required that the load bearing property be, for example, a load bearing capacity high enough to prevent hydrogen leakage from the hydrogen tank even in an unlikely event that the vehicle is destroyed by a collision. To satisfy such a requirement, the casing may be designed, in some cases, by specifications so as to withstand a far greater load (for example, approximately ten times greater) than a collision load which will be input to the hydrogen tank at the occurrence of a side collision. In such cases; i.e., when a robust hydrogen tank is mounted, it is desirable that a phenomenon of getting squashed be prevented from occurring in components around the hydrogen tank, such as the above-described rubber cushioning member, to thereby minimize the extent that a vehicle compartment space is reduced in size in the vehicle width direction.